Olefins are polymerized by using as polymerization catalysts certain novel transition metal complexes of selected bis(carboximidamidatonates).
The polymerization of olefins such as ethylene, propylene, norbornene and cyclopentene are very important commercial processes. These are most commonly done using polymerization catalyst systems containing certain transition complexes. For instance, the Zielger-Natta-type catalysts and metallocene-type catalysts are some of the more important and well-known catalysts of this type which are used to make billions of kilograms of polyolefins annually. Due to the importance of the polymerization of olefins, new catalyst systems are constantly being sought.
Japanese Patent Application 10/36,424 shows a formula for a bis(carboximidamidatonate), but neither describes how to make such a compound nor actually does a polymerization with such a compound.
A. Littke, et al., Organometallics, vol. 17, p. 446-451 (1998); V. Volkis, et al., ibid, p. 3155-3157; J. C. Flores, et al., Organometallics, vol. 14, p. 2106-2108 (1995); P. J. Stewart, et al., ibid, p. 3271-3281; H. W. Roesky, et al., Chem. Ber., vol. 121, p. 1403-1406 (1988); and D. Herskovics-Korine, et al., J. Organometal. Chem., vol. 503, p. 307-314 (1995); report the synthesis and/or use of transition metal complexes of two independent (mono)carboximidamidatonate ligands as polymerization catalysts. However, in none of these references are the two carboximidamidatonates groups joined by a common moiety such as a benzene ring.
A. Littke, et al., Organometallics, vol. 17, p. 446-451 (1998) and S. L. Aelits, et al., ibid, p. 3265-3270, describes the formation of carboximidamidatonates by the reaction of an organometallic compound with a carbodiimide. The use of a bis(alkyl metal salt) to form a bis(carboximidamidatonate) is not described.
This invention concerns a first process for the polymerization of olefins, comprising the step of contacting, at a temperature of about xe2x88x9250xc2x0 C. to about +250xc2x0 C.:
(a) an olefin selected from the group consisting of an xcex1-olefin, a styrene, a cyclopentene, and a norbornene; and
(b) a first compound of the formula (X) 
wherein:
R1, R2, R3 and R4 are each independently hydrocarbyl, substituted hydrocarbyl or silyl;
R15 is a divalent organic moiety;
each X is independently an anion;
n is an integer equal to the valence of M minus 2; and
M is Ti, Zr, Hf, V, Cr, Sc, Y or a rare earth metal.
Optionally, the olefin, first compound and a second compound W may be contacted, which second compound W is a neutral Lewis acid capable of abstracting an Xxe2x88x92 from the first compound to form WXxe2x88x92, provided that the anion formed is a weakly coordinating anion, or a cationic Lewis or Bronsted acid whose counterion is a weakly coordinating anion; and provided that when none of X is alkyl, acyl or hydride, said second compound is capable of transferring hydride or alkyl to M.
This invention also concerns the first compound (X) described above.
In another aspect, the present invention concerns a second process for the polymerization of olefins, comprising the step of contacting, at a temperature of about xe2x88x9250xc2x0 C. to about +250xc2x0 C., a transition metal complex of a ligand of the formula 
with an olefin, wherein:
said olefin is selected from the group consisting of an xcex1-olefin, a styrene, a cyclopentene, and a norbornene;
said transition metal is Ti, Zr, Hf, V, Cr, Sc, Y or a rare earth metal;
R1, R2, R3 and R4 are each independently hydrocarbyl, substituted hydrocarbyl or silyl; and
R15 is a divalent organic moiety.
The present invention further concerns an anion which is the ligand of the formula (XI) described above.
In yet another aspect, the present invention concerns a process for preparing a transition metal complex of a bis(carboximidamidatonate), such as used in the first and second processes described above, comprising the step of reacting a salt of said transition metal with a dialkali metal salt and/or alkaline earth metal salt of a bis(carboximidamidatonate).
Still further, the invention concerns a process for the production of a bis(carboximidamidatonate), comprising the step of reacting a bis(alkyl metal salt) with 2 moles of a carbodiimide.
Herein certain terms are used to define certain chemical groups or compounds. These terms are defined below.
By a carboximidamidatonate group is meant a group of the formula (IX) 
xe2x80x83wherein each R13 is independently hydrocarbyl, substituted hydrocarbyl or silyl. A bis(carboximidamidatonate) has two such groups in the molecule.
By a bis(alkyl metal salt) is meant a compound which has 2 alkyl carbon atoms which each have a single negative charge and are anions of or associated with one or more metal cations in such a way that the positive charge on the metal cation(s) is balanced by the 2 negative charges on the anion.
A xe2x80x9chydrocarbyl groupxe2x80x9d is a univalent group containing only carbon and hydrogen. If not otherwise stated, it is preferred that hydrocarbyl groups herein contain 1 to about 30 carbon atoms.
By xe2x80x9csubstituted hydrocarbylxe2x80x9d herein is meant a hydrocarbyl group which contains one or more substituent groups which are inert under the process conditions to which the compound containing these groups is subjected. The substituent groups also do not substantially interfere with the process. If not otherwise stated, it is preferred that substituted hydrocarbyl groups herein contain 1 to about 30 carbon atoms. Included in the meaning of xe2x80x9csubstitutedxe2x80x9d are heteroaromatic rings. All of the hydrogen atoms in the substituted hydrocarbyl may be substituted for, such as in trifluoromethyl.
By relatively noncoordinating (or weakly coordinating) anions are meant those anions as are generally referred to in the art in this manner, and the coordinating ability of such anions is known and has been discussed in the literature, see for instance W. Beck., et al., Chem. Rev., vol. 88 p. 1405-1421 (1988), and S. H. Stares, Chem. Rev., vol. 93, p. 927-942 (1993), both of which are hereby included by reference. Among such anions are those formed from aluminum compounds such as those described in the immediately subsequent paragraph and Xxe2x88x92, including R193AlXxe2x88x92, R192AlClXxe2x88x92, R19AlCl2Xxe2x88x92, and R19AlOXxe2x88x92, wherein R19 is alkyl. Other useful noncoordinating anions include BAFxe2x88x92 {BAF=tetrakis[3,5-bis(trifluoromethyl)phenyl]borate}, SbF6xe2x88x92, PF6xe2x88x92, and BF4xe2x88x92, trifluoromethanesulfonate, p-toluenesulfonate, (RfSO2)2Nxe2x88x92, and (C6F5)4Bxe2x88x92.
By an alkyl aluminum compound is meant a compound in which at least one alkyl group is bound to an aluminum atom. Other groups such as alkoxide, oxygen, and halogen may also be bound to aluminum atoms in the compound.
By xe2x80x9chydrocarbylenexe2x80x9d herein is meant a divalent group containing only carbon and hydrogen. Typical hydrocarbylene groups are xe2x80x94(CH2)4xe2x80x94, xe2x80x94CH2CH(CH2CH3)CH2CH2xe2x80x94 and 
If not otherwise stated, it is preferred that hydrocarbylene groups herein contain 1 to about 30 carbon atoms.
By xe2x80x9csubstituted hydrocarbylenexe2x80x9d herein is meant a hydrocarbylene group which contains one or more substituent groups which are inert under the process conditions to which the compound containing these groups is subjected. The substituent groups also do not substantially interfere with the process. If not otherwise stated, it is preferred that substituted hydrocarbylene groups herein contain 1 to about 30 carbon atoms. Included within the meaning of xe2x80x9csubstitutedxe2x80x9d are heteroaromatic rings.
By a styrene herein is meant a compound of the formula 
xe2x80x83wherein R26, R27, R26, R29 and R30 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or a functional group, all of which are inert in the polymerization process. It is preferred that all of R26, R27, R26, R29 and R30 are hydrogen.
By xe2x80x9ca norbornenexe2x80x9d is meant that the monomer is characterized by containing at least one norbornene-functional group in its structure including norbornadiene as identified by the formulas below, which can be substituted or unsubstituted 
xe2x80x83wherein xe2x80x9caxe2x80x9d represents a single or double bond. Representative monomers are compounds (VII) and (VIII) as follows: 
xe2x80x83wherein R46, R47, R48, and R49 independently are hydrogen halogen, or hydrocarbyl, provided that, except if the hydrocarbyl group is vinyl, if any of the hydrocarbyl are alkenyl, there is no terminal double bond, i.e., the double bond is internal; or R46 and R48 taken together can be part of carbocyclic ring (saturated, unsaturated or aromatic); or R46 and R47 and/or R48 and R49 taken together are an alkylidene group. In these structures xe2x80x9czxe2x80x9d is 1 to 5. Examples of such norbornenes include norbornadiene, 2-norbornene, 5-methyl-2-norbornene, 5-hexyl-2-norbornene, 5-ethylidene-2-norbornene, vinylnorbornene, dicyclopentadiene, dihydrodicyclopentadiene, tetracyclododecene, trimers of cyclopentadiene, halogenated norbornenes wherein R46, R47, R48 and R49 may also be halogen or fully halogenated alkyl groups such as CwF2w+1 wherein w is 1 to 20, such as perfluoromethyl and perfluorodecyl. The halogenated norbornenes can be synthesized via the Diels-Alder reaction of cyclopentadiene an appropriate dieneophile, such as F3CCxe2x89xa1CCF3 or R492Cxe2x95x90CR49CwF2w+1 wherein each R49 is independently hydrogen or fluorine and w is 1 to 20.
By xe2x80x9csaturated hydrocarbylxe2x80x9d is meant a univalent group containing only carbon and hydrogen which contains no unsaturation, such as olefinic, acetylenic, or aromatic groups. Examples of such groups include alkyl and cycloalkyl. If not otherwise stated, it is preferred that saturated hydrocarbyl groups herein contain 1 to about 30 carbon atoms.
By xe2x80x9cneutral Lewis basexe2x80x9d is meant a compound, which is not an ion, which can act as a Lewis base. Examples of such compounds include ethers, amines, sulfides, and organic nitriles.
By xe2x80x9ccationic Lewis acidxe2x80x9d is meant a cation which can act as a Lewis acid. Examples of such cations are sodium and silver cations.
By xe2x80x9cxcex1-olefinxe2x80x9d is meant a compound of the formula CH2xe2x95x90CHR14, wherein R14 is n-alkyl or branched alkyl, preferably n-alkyl.
By xe2x80x9clinear xcex1-olefinxe2x80x9d is meant a compound of the formula CH2xe2x95x90CHR14, wherein R14 is n-alkyl. It is preferred that the linear xcex1-olefin have 4 to 40 carbon atoms.
By an olefinic bond is meant a carbonxe2x80x94carbon double bond, but does not include bonds in aromatic rings.
By a rare earth metal is meant one of lanthanum, cerium, praeseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium or lutetium.
By a functional group is meant a group which does not interfere with the stability synthesis of, or functioning of a compound. Suitable functional groups may include (depending on which compound they are in) ether, halo, siloxy, silyl, ester, fluoroalkyl, fluorosulfonyl, and tertiary amino.
By a divalent organic moiety is meant a divalent group in which the free valences are to two different atoms in the group, and which contains at least one carbon atom. This moiety may contain one or more heteroatoms, preferably nitrogen or silicon. One or both of the free valencies may be to heteroatoms (as opposed to carbon atoms). Preferably both free valencies are to carbon atoms or nitrogen atoms, more preferably to carbon atoms.
By a silyl group is meant a group of the formula xe2x80x94SiR16R17R18, wherein R16, R17 and R18 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or a functional group.
The bis(carboximidamidatonates) can generally be made by the following method. A dialkali metal or alkaline earth metal salt is prepared, such as is shown in equation (1), from a suitable dihalogen compound or other suitable precursor. Such reactions to prepare these types of organometallic compounds are known in the art to prepare, for example, dilithium or dimagnesium compounds, see for instance G. Wilkinson, et al., Ed., Comprehensive Organometallic Chemistry, Pergamon Press, Oxford, 1982; J. Klein, et al., Tetrahedron, vol. 132, p. 51 (1976); and M. F. Lappert, et al., J. Chem. Soc. Chem. Commun, p. 14 (1982). The dialkali metal salt or alkaline earth metal salt is then reacted with 2 moles of a carbodiimide to form the corresponding alkali or alkaline earth metal salt of the bis(carboximidamidatonate), as shown in equation (2). The product of equation (2) is then reacted with a salt of an appropriate transition metal to form the transition metal complex of the bis(carboximidamidatonate) which may be used in the polymerization catalyst system. The use of a bis(carboximidamidatonate) (particularly the compound with a nontransition metal, such as an alkali metal or magnesium) to react with the salt of a transition metal is also novel, and preferably takes place in solution at a temperature of about xe2x88x9250xc2x0 C. to about +100xc2x0 C. By using appropriate groups or substituents on the various reactants, substituted bis(carboximidamidatonates) with different groups may be formed. Equations (1), (2) and (3) just illustrate one particular method of making these compounds. 
In (X) and (XI) useful groups for R15 include, for example, xe2x80x94CR162(CR162)qCR162xe2x80x94 (XV), wherein each R16 is independently hydrogen, hydrocarbyl or substituted hydrocarbyl and q is 0 or an integer from 1 to 20, especially q is 4. Other useful groups for R15 include, for example, o-phenylene, 1,2-naphthylene, 2,3-naphthylene, 1,8-naphthylene, 1,2-cyclohexylene, 
wherein R5, R6, R7 and R8 are each independently hydrogen, hydrocarbyl or substituted hydrocarbyl, provided that either or both of the pairs R5 and R6, and R7 and R8 taken together may form a ring; and R9, R10, R11 and R12 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or a functional group, provided that any two of R9, R10, R11 and R12 vicinal to one another may form a ring. Preferred groups for R15 are (XII), (XV) wherein q is 2 and/or each R16 is hydrogen, (XV) in which q is 1, each R16 on the terminal carbon atoms is hydrogen, and both R16 groups on the middle carbon atom are methyl [xe2x80x94H2CC(CH3)2CH2xe2x80x94], and (XII), with (XV) being especially preferred. It is also preferred that R15 contain at least two carbon atoms, and that each of the free valencies of R15 are to different carbon atoms.
In another especially preferred embodiment of (X) and (XI), R15 is (XII) or (XXIII) and the total compounds [when R15 is (XII)] are of the formulas 
In (I), (III), (X), (XI), (XII), as appropriate it is preferred that:
R1, R2, R3 and R4 are each independently alkyl or silyl, more preferably alkyl containing 1 to 6 carbon atoms; and/or
R1, R2, R3 and R4 are all the same; and/or
R5, R6, R7 and R8 are each independently hydrogen or alkyl, more preferably all are hydrogen; and/or
R9, R10, R11 and R12 are all hydrogen; and/or
one or more of R9, R10, R11 and R12 are alkyl, aryl or substituted aryl.
In compounds such as (I) and (X) preferred transition metals are Zr, Ti, V and Hf, and Zr and Ti are more preferred. Preferred metal oxidation states are Ti[II, III, and IV], Zr[II and IV], Hf[IV], V[IV and V], Cr[III], Sc[III], Y[III] and the rare earth metals[III]. When lower oxidation states of the metals are employed, it may beneficial to include an oxidant in the catalyst activation step. This may be an alkyl halide to provide simultaneous alkylation if the compound is not prealkylated, or a standard oxidant such as oxygen when another alkylating agent is used. In compounds in which silyl groups are present it is preferred that R16, R17 and R18 are each independently alkyl or aryl, more preferably alkyl, and especially preferably all are methyl.
Anions X may have one negative charge (monoanion), or more than one negative charge (dianion, etc.). The number of anions, X, which corresponds to n, can be a fractional number or a whole number, depending on the number of residual positive charges on the ligand plus metal cation. For example if the metal valence is 3, and the anion is a dianion (Xxe2x88x922), then n would be 0.5. Preferred anions are monoanions. Useful anions include acyl, alkoxide, hydride, halide, carboxylate, alkyl such as methyl, benzyl, neopentyl, neophyl, and trimethylsilylmethyl, and preferred anions are halide, especially chloride and bromide, and alkyl.
Included within the meaning of a compound of formula (I) are compounds of the formula 
wherein R1 through R12, M, X and n are as described above and Z is a monovalent anion. This is simply a representation of (I) in which one of the anions X is not xe2x80x9cboundxe2x80x9d to the metal cation. Usually Z is a relatively noncoordinationg anion.
Useful olefins for polymerization include one or more of ethylene, propylene, 1-butene, 1-hexene, 1-octene, styrene, norbornene, other xcex1-olefins, cyclopentene and alkyl substituted cyclopentenes. Copolymers, such as copolymers of ethylene and one or more xcex1-olefins may also be made. Preferred olefins are one or more of ethylene, propylene and a linear xcex1-olefin.
The second compound in the first polymerization process (and also useful in the second polymerization process), W, is a neutral Lewis acid that can abstract Xxe2x88x92 from (I) or (X) to form WXxe2x88x92. Useful Lewis acids for this abstraction include B(C6F5)3, AlCl3, MgCl2 and alkyl aluminum compounds such as methyl aluminoxane, diethylaluminum chloride and ethylaluminum chloride. If a hydrocarbyl anion, preferably an alkyl anion, more preferably a methyl anion, or a hydride anion, is not bound to the metal atom of (I), W (or another W) must also transfer a hydrocarbyl (preferably an alkyl) or hydride anion to the metal atom. Essentially the same effect can be obtained by using one molecule of the alkyl aluminum compound to place an alkyl group on the metal, and another molecule to abstract the X anion. Preferred neutral Lewis acids for transferring a hydrocarbyl group to the metal atom are alkyl aluminum compounds. Suitable alkyl aluminum compounds include alkyl aluminum sesquioxides [(R18AlO)n], especially wherein R18 is methyl. Alkyl aluminum sesquioxides are preferred alkyl aluminum compounds. W can also constitute a mixture of two compounds, a strong Lewis acid such as B(C6F5)3 and an alkylating agent such as triethylaluminum. A stoichiometric or larger amount of the neutral Lewis acid is preferred, and a more preferred molar ratio of W:(I) is about 1 to about 10,000, preferably about 10 to about 5,000.
In the first and second polymerization processes herein, the temperature at which the polymerization is carried out is about xe2x88x9250xc2x0 C. to about +250xc2x0 C., preferably about xe2x88x9260xc2x0 C. to about 150xc2x0 C., more preferably about xe2x88x9220xc2x0 C. to about 100xc2x0 C. The pressure of the olefin (if it is a gas) at which the polymerization is carried out is not critical, atmospheric pressure to about 275 MPa being a suitable range.
The polymerization processes herein may be run in the presence of various liquids, particularly aprotic organic liquids. The catalyst system, olefin, and polymer may be soluble or insoluble in these liquids, but obviously these liquids should not prevent the polymerization from occurring. Suitable liquids include alkanes, cycloalkanes, selected halogenated hydrocarbons, and aromatic hydrocarbons. Specific useful solvents include hexane, toluene, benzene methylene chloride, and 1,2,4-trichlorobenzene.
The olefin polymerizations herein may also initially be carried out in the solid state by, for instance, supporting the transition metal compound on a substrate such as silica or alumina, activating it with the Lewis (such as W, for instance an alkylaluminum compound) or Bronsted acid and exposing it to the olefin. Alternatively, the support may first be contacted (reacted) with W such as an alkylaluminum compound, and then contacted with an appropriate transition metal compound such as (I) or (X). The support may also be able to take the place of the Lewis or Bronsted acid, for instance an acidic clay such as montmorillonite. Another method of making a supported catalyst is to start a polymerization or at least make a transition metal complex of another olefin or oligomer of an olefin such as cyclopentene on a support such as silica or alumina. These xe2x80x9cheterogeneousxe2x80x9d catalysts may be used to catalyze polymerization in the gas phase or the liquid phase. By gas phase is meant that a gaseous olefin is transported to contact with the catalyst particle.
In all of the polymerization processes described herein oligomers and polymers of the various olefins are made. They may range in molecular weight from oligomeric olefins, to lower molecular weight oils and waxes, to higher molecular weight polyolefins. One preferred product is a polymer with a degree of polymerization (DP) of about 10 or more, preferably about 40 or more. By xe2x80x9cDPxe2x80x9d is meant the average number of repeat (monomer) units in a polymer molecule.
Depending on its properties, the polymer made by the processes described herein is useful in many ways. For instance if it is a thermoplastic, it may be used as a molding resin, for extrusion, film, etc. If it is elastomeric, it may be used as an elastomer.
Polyolefins are most often prepared by polymerization processes in which a transition metal containing catalyst system is used. Depending on the process conditions used and the catalyst system chosen, polymers, even those made from the same monomer(s) may have varying properties. Some of the properties which may change are molecular weight and molecular weight distribution, crystallinity, melting point, and glass transition temperature. Except for molecular weight and molecular weight distribution, branching can affect all the other properties mentioned.
It is known that certain transition metal containing polymerization catalysts including those disclosed herein, are especially useful in varying the branching in polyolefins made with them, see for instance World Patent Applications 96/23010, 97/02298, 98/30609 and 98/30610. It is also known that blends of distinct polymers, that vary for instance in the properties listed above, may have advantageous properties compared to xe2x80x9csinglexe2x80x9d polymers. For instance it is known that polymers with broad or bimodal molecular weight distributions may be melt processed (be shaped) more easily than narrower molecular weight distribution polymers. Similarly, thermoplastics such as crystalline polymers may often be toughened by blending with elastomeric polymers.
Therefore, methods of producing polymers which inherently produce polymer blends are useful especially if a later separate (and expensive) polymer mixing step can be avoided. However in such polymerizations one should be aware that two different catalysts may interfere with one another, or interact in such a way as to give a single polymer.
In such a process the catalysts disclosed herein can be termed the first active polymerization catalyst. Monomers useful with these catalysts are those described (and also preferred) above.
A second active polymerization catalyst (and optionally one or more others) is used in conjunction with the first active polymerization catalyst. The second active polymerization catalyst may be a late transition metal catalyst, for example as described in World Patent Applications 96/23010, 97/02298, 98/27124, 98/30609, 98/30610 and 98/30612. Other types of catalysts may also be used for the second active polymerization catalyst. For instance so-called Ziegler-Natta and/or metallocene-type catalysts may also be used. These types of catalysts are well known in the polyolefin field, see for instance Angew. Chem., Int. Ed. Engl., vol. 34, p. 1143-1170 (1995), European Patent Application 416,815 and U.S. Pat. No. 5,198,401 for information about metallocene-type catalysts, and J. Boor Jr., Ziegler-Natta Catalysts and Polymerizations, Academic Press, New York, 1979 for information about Ziegler-Natta-type catalysts, all of which are hereby included by reference. Many of the useful polymerization conditions for all of these types of catalysts and the first active polymerization catalysts coincide, so conditions for the polymerizations with (I) or (X) are easily accessible. Oftentimes the xe2x80x9cco-catalystxe2x80x9d or xe2x80x9cactivatorxe2x80x9d is needed for metallocene or Ziegler-Natta-type polymerizations. In many instances the same compound, such as an alkylaluminum compound, may be used as an xe2x80x9cactivatorxe2x80x9d for some or all of these various polymerization catalysts.
In one preferred process described herein the first olefin(s) [the monomer(s) polymerized by the first active polymerization catalyst] and second olefin(s) [the monomer(s) polymerized by the second active polymerization catalyst] are identical, and preferred olefins in such a process are the same as described immediately above. The first and/or second olefins may also be a single olefin or a mixture of olefins to make a copolymer. Again it is preferred that they be identical particularly in a process in which polymerization by the first and second active polymerization catalysts make polymer simultaneously.
In some processes herein the first active polymerization catalyst may polymerize a monomer that may not be polymerized by said second active polymerization catalyst, and/or vice versa. In that instance two chemically distinct polymers may be produced. In another scenario two monomers would be present, with one polymerization catalyst producing a copolymer, and the other polymerization catalyst producing a homopolymer, or two copolymers may be produced which vary in the molar proportion or repeat units from the various monomers. Other analogous combinations will be evident to the artisan.
In another variation of this process one of the polymerization catalysts makes an oligomer of an olefin, preferably ethylene, which oligomer has the formula R70CHxe2x95x90CH2, wherein R70 is n-alkyl, preferably with an even number of carbon atoms. The other polymerization catalyst in the process them (co)polymerizes this olefin, either by itself or preferably with at least one other olefin, preferably ethylene, to form a branched polyolefin. Preparation of the oligomer (which is sometimes called an xcex1-olefin) by a second active polymerization-type of catalyst can be found in World Patent Applications 96/23010 and 98/30612.
Likewise, conditions for such polymerizations, using catalysts of the second active polymerization type, will also be found in the appropriate above mentioned references.
Two chemically different active polymerization catalysts are used in this polymerization process. The first active polymerization catalyst is described in detail above. The second active polymerization catalyst may also meet the limitations of the first active polymerization catalyst, but must be chemically distinct. For instance, it may have a different transition metal present, and/or utilize a different type of ligand and/or the same type of ligand which differs in structure between the first and second active polymerization catalysts. In one preferred process, the ligand type and the metal are the same, but the ligands differ in their substituents.
Included within the definition of two active polymerization catalysts are systems in which a single polymerization catalyst is added together with another ligand, preferably the same type of ligand, which can displace the original ligand coordinated to the metal of the original active polymerization catalyst, to produce in situ two different polymerization catalysts.
The molar ratio of the first active polymerization catalyst to the second active polymerization catalyst used will depend on the ratio of polymer from each catalyst desired, and the relative rate of polymerization of each catalyst under the process conditions. For instance, if one wanted to prepare a xe2x80x9ctoughenedxe2x80x9d thermoplastic polyethylene that contained 80% crystalline polyethylene and 20% rubbery polyethylene, and the rates of polymerization of the two catalysts were equal, then one would use a 4:1 molar ratio of the catalyst that gave crystalline polyethylene to the catalyst that gave rubbery polyethylene. More than two active polymerization catalysts may also be used if the desired product is to contain more than two different types of polymer.
The polymers made by the first active polymerization catalyst and the second active polymerization catalyst may be made in sequence, i.e., a polymerization with one (either first or second) of the catalysts followed by a polymerization with the other catalyst, as by using two polymerization vessels in series. However it is preferred to carry out the polymerization using the first and second active polymerization catalysts in the same vessel(s), i.e., simultaneously. This is possible because in most instances the first and second active polymerization catalysts are compatible with each other, and they produce their distinctive polymers in the other catalyst""s presence. Any of the processes applicable to the individual catalysts may be used in this polymerization process with 2 or more catalysts, i.e., gas phase, liquid phase, continuous, etc.
The polymers produced by this process may vary in molecular weight and/or molecular weight distribution and/or melting point and/or level of crystallinity, and/or glass transition temperature and/or other factors. For copolymers the polymers may differ in ratios of comonomers if the different polymerization catalysts polymerize the monomers present at different relative rates. The polymers produced are useful as molding and extrusion resins and in films as for packaging. They may have advantages such as improved melt processing, toughness and improved low temperature properties.
Hydrogen may be used to lower the molecular weight of polyolefin produced in the first or second processes. It is preferred that the amount of hydrogen present be about 0.01 to about 50 mole percent of the olefin present, preferably about 1 to about 20 mole percent. When liquid monomers (olefins) are present, one may need to experiment briefly to find the relative amounts of liquid monomers and hydrogen (as a gas). If both the hydrogen and monomer(s) are gaseous, their relative concentrations may be regulated by their partial pressures.
In the Examples, the following abbreviations are used:
xcex94Hf xe2x80x94heat of fusion (of polymer)
Cyxe2x80x94cyclohexyl
GPCxe2x80x94Gel Permeation Chromatography
MIxe2x80x94melt index
Mnxe2x80x94number average molecular weight
Mwxe2x80x94weight average molecular weight
PExe2x80x94polyethylene
PMAOxe2x80x94poly(methylaluminoxane)
PMAO-IP xe2x80x94see PMAO
PPxe2x80x94polypropylene
Prxe2x80x94propyl
RTxe2x80x94room temperature
THFxe2x80x94tetrahydrofuran
In the Examples, all pressures are gauge pressures.
xe2x80x9cMe/1000 CH2xe2x80x9d is the total number of methyl groups per 1000 methylene groups in the polymer and is measured by 1H NMR. For method of NMR measurement and calculations, see World Patent Application 96/23010.
Differential Scanning Calorimetry was used to measure polymer melting points (Tm in xc2x0 C., taken as the peak of the melting endotherm), and heat of fusion (xcex94Hf in J/g), using a heating rate of 10xc2x0 C./min. Results reported are from the second heat.
The dimagnesium reagents were prepared according to the procedure of M. F. Lappert and T. R. Martin, J. Chem. Soc. Dalton Trans. 1982, 1959. Excess magnesium metal was reacted with dichloro or dibromo-hydrocarbon compounds in THF at RT to yield a high yield of the dimagnesium reagents which were then reacted with 1 equiv of the carbodiimide in THF at RT for 2-3 days. The solvent was removed in vacuo and the crude products were washed with pentane to give a white powder product.